Provisioning and growth rates of nestling Fulmars Fulmarus glacialis: stochastic variation or regulation?

Abstract

The pattern of chick feeding in the Fulmar Fulmarus glacialis at St Kilda, Scotland, was examined by repeated weighing of chicks throughout 14 consecutive days during the first half of the chick-rearing period in 1994. After correcting for metabolic weight losses, the sizes of positive mass increments between weighings were used to assess meal sizes and feeding frequency for each chick. Individual meals fed to chicks averaged 80.8 g (s.d. t 21.0 g), or approximately 10% of adult mass. Each chick received 0 to 4 meals per day, with an average of 1.9 meals per chick per day, giving an average interval of around 2 5 h between meals delivered by each parent. The distribution of time intervals between feeds for each chick (whether single or double meals) followed a negative exponential function with a maximum value of 80 h. These results are not compatible with the idea that the purpose of large fat deposits in procellariiform chicks is to guarantee survival over long intervals between feeds. Over 14 days, the chicks' mean daily food requirements for zerogrowth increased from 9 8 g to 160 g. This corresponded with a n increase in feeding frequency but not meal size. Chicks with lower scores for body condition after feeding by both parents received more meals during the subsequent 16 h and had shorter intervals to the next feed, indicating that adults regulated feeding frequency in accordance with chick condition at the previous feed. This does not agree with the hypothesis that lipid accumulation by nestling Procellariiformes is a response to stochastic variation in food delivery associated with an absence of regulation. In view of the diversity of growth and feeding patterns present among the Procellariiformes, it is possible that lipid accumulation in this group does not have a unitary explanation.

Chick provisioning by the Yellow‐nosed Albatross Diomedea chlororhynchos: response of foraging effort to experimentally increased costs and demands

“…Although several studies have suggested that chick provisioning is not regulated according to the needs of the chick but, rather, is maximized through an intrinsic rhythm (Ricklefs 1987, Hamer & Hill 1993, Saether et al 1993, Ricklefs & Schew 1994, others indicate that parents could respond to chick needs (Bolton 1995, Weimershrch et al 1995, 1997b, Hamer & Thompson 1997. These inconsistencies may arise from different causes.…”

Growth and provisioning strategies of Northern Fulmars Fulmarus glacialis

“…There were no differences in mean mass or in the rate of mass gain between chicks weighed at frequent intervals and the large sample of control chicks weighed only three times during the season (see Results). Nor have previous studies on procellariiforms identified deleterious effects of repeated weighing on chick body condition (Hamer 1994, Hamer & Thompson 1997, Granadeiro et al 1998. We can therefore be confident that the procedures used in this study produced reliable results.…”

“…Although rates of mass loss after feeding follow a negatibe exponential curve over long periods, mass loss in Fulniar chick is approximately linear for a t least 8 h following meal (Hamer & Thompson 1997) Equation 1 aboie was therefore used to calculate expected mass at the end of each 6 or 8 h interval, and the chick was assumed to have been fed if its observed mass was 20 g or more above the value predicted in the absence of feeding (Phillips & Hamer 2000). This approach allowed the correct prediction of over 96% of observed feeds (Phillips & Hamer 2000).…”

“…Previous research on the foraging ecology of Northern Fulmars has involved either the monitoring of adult attendance for a limited period or the indirect assessment of feeding frequency and meal mass using repeated weighing (Furness & Todd 1984, Hamer & Thompson 1997, Hamer et al 1997a). However, no study has used both methods in conjunction, and previous work was all carried out when chicks were less than half-grown.…”

Automated techniques for measuring meal size in great albatrosses

“…Periodic weighing of seabirds, especially chicks, has been used often as a research method in studying chick provisioning of Procellariiformes seabirds (albatrosses, shearwaters and petrels) (Hamer & Thompson 1997;Weimerskirch et al 1997aWeimerskirch et al , 1997bPhillips & Hamer 2000;Weimerskirch & Lys 2000;Phillips & Croxall 2003). However, hand-weighing is labour-intensive and the repeated handling of birds can disrupt breeding, limiting the ability to conduct detailed studies that require frequent weighing to collect a longer time series of data.…”